1. Field of the Invention
The present invention pertains to movable irrigation systems, and more particularly, it pertains to irrigation systems which are arranged to be connected to a fixed water supply source and which are arranged to be moved in a predetermined path under power supplied by the water pressure therein to irrigate relatively large areas of land.
2. Description of the Prior Art
In those areas which receive little or no rainfall over extended periods of time, such as in the western portion of the United States, it is a common practice to water crops by means of movable irrigation systems. Typically, such irrigation systems comprise a string of interconnected pipe sections having sprinkler heads, or other water spreading means, arranged at spaced intervals along the length thereof and with support wheels being provided for the pipe sections at generally uniformly spaced intervals along the length thereof. The wheels may be arranged to support the pipe sections so that they pass through the axes of the wheels, or the wheels may be mounted on carriages for supporting the pipe sections at an offset position. In either case, the pipe sections and their associated sprinkler heads are supported at a fixed distance above the ground so that they will be above the crop which is to be irrigated. Some means is typically provided to move the string of pipe sections along the area to be sprinkled with the wheels rolling along in predetermined tracks. This movement can either be linear or it can be rotary, i.e., the pipe string can rotate about a central pivot axis where an upstanding water supply pipe is located to which one end of the pipe string is attached.
In the aforementioned rotary movement type of irrigation system, the interconnected string of pipe sections extends radially from the water supply pipe and is driven either by means of the carriages which support the pipe sections at spaced intervals therealong or by means of a single power mover connected to the string of pipe sections at or near the outer end thereof, a typical example of the latter arrangement being shown in U.S. Pat. No. 3,536,251 to Van den Brink. The power for the single power mover means may be provided by an electric battery, a gasoline driven engine, or through an electric power line running along the length of the irrigation tubing and connected to an electric outlet at the inner, fixed end thereof. Alternatively, the power mover may be powered directly through the water pressure in the pipe section.
The latter drive arrangement, wherein no source of power other than the water supply under pressure is needed, is obviously advantageous. Such a system has been found to be workable as the drive means must be geared to operate at a very low ground speed so that the total area being irrigated will be provided with sufficient water. Typically, the string of interconnected pipe sections makes one complete revolution in the time normally required between waterings (about eight days); hence, the entire length of irrigation tubing need only be continuously driven at a rate so as to make one revolution about the central water supply pipe every eight days.
Hydraulically powered drive means for rotary irrigation systems, which operate under the water pressure in the irrigation tubing, may be located at the single power mover connected at the end of the tubing, or they may be located at each of the support carriages along the length thereof. Such systems may comprise a basic water wheel geared down to move the tubing at a very low rate, or they may comprise cylinder and piston arrangements which drive in only one direction. For example, the United States patent to de Laine et al U.S. Pat. No. 3,730,211 discloses the latter type of apparatus wherein an elongate tubing is connected at one end to water under pressure and at the other end to an hydraulic towing device, such device comprising a cylinder housing a piston having a piston rod which extends from the cylinder, valve means operable to cause the water under pressure to reciprocate the piston within the cylinder, and a one-way linkage connected to the piston rod for preventing the movement of the cylinder and the piston rod in one and the same direction so that the towing device moves in a forward direction only.
Other prior United States patents which show hydraulic cylinder and piston devices for moving irrigation tubing wherein such devices operate under the power supplied by the flow of irrigation water in the tubing include U.S. Pat. No. 2,893,643 to Gordon and U.S. Pat. No. 3,259,319 to Wallace.